[Feature Request] Add scrolling/expansion for truncated AskUserQuestion preview panes

Bug Description
Title: No way to view hidden lines in AskUserQuestion preview pane Body: When an AskUserQuestion option includes a preview longer than the available terminal height, the preview pane truncates with a ─── ✂ ─── N lines hidden ───── marker and there's no documented keybinding to expand, scroll, or pop it into fullscreen. Workarounds today: not found Requested: a single-key shortcut to expand the focused option's preview into a fullscreen overlay, or scrollability within the preview pane (e.g. j/k or PgUp/PgDn while focused).

Environment Info

• Platform: linux
• Terminal: pycharm
• Version: 2.1.139
• Feedback ID: 9ab6938f-4f78-4843-b646-032c2ce4c67d

Errors

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